Treatment of leather with methylpolysiloxanes



United Stats TREATR libl'll t'lF WHTH METHYL PQLYSHJGXANES Edgar D. Brown, Jr., Schenectady, N. Y., assignor to Gen= oral Electric Company, a corporation of New York No Drawing, Application February 3, H54, erial No. 409,001

12 Claims. (G. Edd-293) This invention is concerned with obtaining leathers having improved properties. More particularly, the invention relates to a process for improving the water repellency, washability, flexing characteristics, and the feel of leather, which process comprises treating the latter with an aqueous emulsion substantially free of organic solvents and containing as the essential treating agent a mixture of ingredients composed primarily of (a) the curable, non-resinous, fluid product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by weight, of 50 to 75% dimethylchlorosilane, 1 to trimethylchlorosilane, 10 to methyltrichlorosilane, and up to 10% of a methylchlorodisilane and (b) a curing agent for (a) comprising a metallic salt of organic and inorganic acids whose metal ion is present, b weight, based on the weight of the curable hydrolysis product in an amount equal to from 2 to 14%, the amount of the said curable hydrolysis product ranging from 0.2 to 20%, by weight, of the total weight of the aqueous emulsion. The invention also includes leather treated in accordance with the above-recited process.

Various means have been employed in the past to impart to various types of leather improved abrasion resistance, increased water repellency without harming the air permeability thereof, and improved feel or hand, while at the same time improving the washability without loss of the desirable properties present in the leather before washing. One of the present methods for accomplishing this is to treat the leather with various waxes such as paraflin waxes or with metallic salts of long-chain aliphatic acids, such as aluminum stearate, aluminum oleate. However, the use of such waxes or metallic salts of long-chain aliphatic fatty acids has not been too satisfactory because of the fact that after one washing, essentially all the water-repellent characteristics are lost and, in addition to being unable to withstand dry cleaning, the appearance of the leather is undesirably affected upon contact with excessive amounts of water, even though there is present therein the particular waxy or metallic salt water repellent. Moreover, the presence of certain waxes and metallic salts often stiffens the surface of the leather and prevents the passage of water vapor and other gases, such as air, to an undesirable degree.

Many organopolysiloxanes, particularly organopolysiloxane fluids and resins, have been tried in combination with leather treatment, but these, again, have not been satisfactory since it has been found that they easily leached out when the treated leather came in contact with water, or excessive amounts of the organopolysiloxane are necessary to be incorporated in the leather before any satisfactory degree of water repellency is obtained. Moreover, it has also been found that these organopolysiloxane resins rupture readily after undesirably short periods of flexing and films of such resins when applied to leather have low abrasion resistance.

In addition, itihas also been determined that the feel or handle of the leather is undesirably affected and that the ability to suede leather after treatment with. heretofore employed organopolysiloxanes is materially reduced. Certain of these organopolysiloxanes have been found to actually interfere with this ability to suede the leather by depositing an oily or sticky film thereon so that a sueding operation cannot be carried out with any satisfactory degree of success. Finally, it has been found that organic solvents are usually necessary to use in combination with these organopolysiloxane fluids in the treating medium, and these organic solvents, in addition to introducing hazardous and toxic conditions, also have a deleterious effect on the properties of the leather. Investigators in this field have stated in the past that attempts to use organopolysiloxanes hereofore employed for the purpose in the form of aqueous emulsions without organic solvents has imparted poor water repellency and that a more desirable level of water repellency is only obtainable by the use of solvents but accompanied by the disadvantages recited above.

A still further class of organosilicon compositions which has been suggested in the past for treating leather to improve its properties includes ammonolyzed compounds of organohalosilanes containing a grouping where R is a member selected from the class consisting of hydrogen and monovalent hydrocarbon radicals, in place of the oxygen of the siloxane linkages of organopolysiloxanes. These silicon amine resins are more particularly described in Cheronis Patent 2,635,059 and Cheronis et al. Patent 2,635,060. However, these silicon amine resins had not been satisfactory for several reasons. One is due to the fact that organic solvents are essential in preparing the treating mixture. Again, it has been reported that these silicon amine resins are not satisfactorily permeable to water vapor and the flexibility of leather is not improved by means of treatment with the silicon amine resins.

I have now discovered that a particular type of methylpolysiloxane hydrolysis product obviates all the defects recited above and, in addition, imparts new advantages nowhere obtainable by any of the materials heretofore used for the same purpose. By means of my newly discovered treatment, I am able to obtain leathers which can be washed and dry cleaned several times without any undesirable reduction in water-repellent properties, and with scarcely any change in the feel or handle of the leather. As a matter of fact, the feel and texture of the leather appear to be improved as a result of the treatment with the aforesaid methylpolysiloxane hydrolysis product. Moreover, contrary to the experience encountered when using other types of organopolysiloxanes, the leather surface remains essentially unchanged and can be readily sueded to give outstanding products whose surfaces again are still water-repellent. Again, by means of my treating process, scarcely any change in water or gaseous premeability is encountered, and what is even more significant, the treated leather remains highly water-repellent, even under extreme conditions of twisting and flexing. As

an additional feature resulting from the practice of my process, the water repellency unexpectedly remains essentially the same even when forcibly wetted. Also, it

has been found that the dimensional stability of leather treated in accordance with my process and thereafter washed, even after about eight times, is scarcely changed.

As a still further advantage of using my process, the

wet crocking (tendency of the color to rub off when abraded) tendencies of the finished or dyed leather are materially reduced. These results are all accomplished by employing aqueous emulsions substantially free of any.

organic solvent and are attainable even though the organopolysiloxane pickup, based on the dry weight of the leather, is materially below for instance, as low as ,2 to 6%, or even lower, depending on the degree of water repellency, anti-crocking, dimensional stability, etc. desired. This should be contrasted with the requirements of pickup for other types of organosilicon compositions, which generally are within the range of from about to 30%.

All the foregoing desirable results and improved properties are attainable by employing in the treating mixture a specific type of methylpolysiloxane obtained by the hydrolysis of acertain combination of ingredients in particular proportions. The methylpolysiloxane used and found to be so eminently suitable for this purpose comprises a polymerizable, fluid, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by weight, of 50 to 75% dimethyldichlorosilane, l to 10% trimethylchlorosilance, 10 to 35% methyltrichlorosilane and from about 1 to 10% of a methylchlorodisilane (or mixture of methylchlorodisilanes). The methylchlorodisilane or mixture of methylchlorodisilanes may be in the form of tetrachlorodimethyldisilane, pentachloromethyldisilane, trichlorotrimethyldisilane, dichlorotetramethyldisilane, etc., or mixtures of these methylchlorodisilanes, either alone or with hexachlorodisilane. Generally, these methylchlorodisilanes may comprise from about 1 to as high as 12% of the mixture of methylehlorosilanes. In combination with this air and heat-curable hydrolysis product, it is essential for optimum practice of the invention to employ a curing agent for the hydrolysis product comprising a metallic salt of an organic or inorganic acid.

The intermediate hydrolyzable mixture of methylchlorosilanes is generally obtained by passing methyl chloride over silicon in the presence of copper at elevated temperatures in a manner disclosed and claimed in Rochow Patent 2,380,995, issued August 7, 1945 and assigned to the same assignee as the present invention. The reaction product thus obtained, in addition to containing the above-described methylchlorosilanes in the stipulated proportions, also contains small amounts of silicon tetrachloride, tetramethylsilane, hexamethyldisilane, methyl-substituted polysilanes containing more than two silicons attached by silicon-silicon linkages, etc. These additional ingredients are present generally in insignificant amounts and may be removed, if desired, from the hydrolyzable mixture prior to effecting conversion to the methylpolysiloxane state. The usual methods of hydrolysis with water are employed and it is generally desirable to neutralize the HCl formed and to wash the hydrolysis product sufficiently to obtain an essentially neutral product. Advantageously, non-interpolymerized components, such'as hexamethyldisiloxane and octamethylcyclotetrasiloxane, and products boiling below 100 (3., present in the hydrolysis product are removed from the latter.

The curing agents used for the above hydrolysis product (for brevity hereinafter referred to as methylpolysiloxane) are those capable of eflecting cure of the methylpolysiloxane without deleterious etfect on the leather treating mixture or on the leather itself. These metallic salts (for brevity hereinafter so referred to) may be either water-soluble or soluble in the methylpolysiloxane. Where it is desired that the material being treated should be free of any color change due to any coloring in the treating composition, the metallic salt should itself be free of extraneous color, either when employed in the emulsion or dispersion form of treating mixture, .or when present on the treated material.

Various classes of metallic salts satisfying the requirements recited above may be employed. One class of such salts comprises metallic salts, particularly the watersoluble metallic salts, in which the metal ion is derived from Group IV in the Periodic Table. Among such 4 v metallic salts may be mentioned the water-soluble salts (both inorganic and metallo-organic) of, for instance, titanium, zirconium, tin, lead, etc., such as zirconium tetrachloride, zirconium oxychloride (including its hydrates), zirconium sulfate, and hydrates, zirconium acetate, zirconium nitrate, zirconium ammonium carbonate, zirconium oxybromide, stannous chloride, stannic chloride, zinc acetate, zinc nitrate, nickel sulfate, nickel acetate, nickel chloride, titanium oxychloride, titanium nitrate (TiO-N2O5'6H2O), titanium oxalate lead chloride, etc. Various complexes, both organic and inorganic, of these metallic salts may be employed without departing from the scope of the invention. Among such complexes may be mentioned, for instance, complexes formed by treating zirconium hydroxide with mannitol in a dilute base such as, for instance, sodium hydroxide, zirconium oxalate having the formula etc. Also, hydrates of the various metallic salts described generically and specifically above may also be employed.

In addition to the water-soluble salts mentioned above which are preferred, one may also employ water-insoluble metallic salts which are soluble in the o-rganopolysiloxane or which can be readily dispersed or emulsified with the methylpolysiloxane, so as to be in intimate contact with the latter in order to exercise their curing function. Among the metallic salts which are soluble in the methylpolysiloxane are, for example, metallic salts of organic acids, for instance, acid radicals yielding the resinate, linoleate, stearate, oleate, or even the lower acid radicals such as those yielding butyrate, octoate, hexoate, etc. radicals as well as naphthenate salts. The prime requisite for such types of metallo-organic salts is that they be soluble in some medium such as the organopolysiloxane or water, or be capable of being intimately dispersed or suspended so as to bring them into intimate contact with the methylpolysiloxane so as to permit the metallic salt to exercise its curing function. Examples of such salts are, for instance, zinc naphthenate, zinc octoate, tin oetoate, tin naphthenate, etc. The prime requisite in the selection of the metallic salt is that it exert a curing effect upon the m-ethylpolysiloxane either at room temperature or at elevated temperatures at which the treating composition is converted on the surface of the leather in its final form.

The amount of metallic salt which may be used may be varied widely without departing from the scope of the invention. Thus, on a weight basis, and based on the weight of the methylpolysiloxane, the metal in the metallic salt may comprise at least 2%, e. g., from about 2 to 14%, or more, optimum results generally being obtained in the range of from about 5 to 12%, by weight. Based on the weight of the methylpolysiloxane, the total metallic salt advantageously comprises from 6 to 42%, by weight. The amount of metallic salt employed will depend upon such factors as, for instance, the particular metal salt used, including the metal ion), the particular type of methylpolysiloxane employed includ-- ing its constitution prior to hydrolysis thereof, the type of leather to which the treating composition will be applied, the solubility of the metallic salt as well as the medium in which the metallic salt will be used, the treating conditions including the temperature and time of treatment, the stability of the emulsion, etc.

In the practice of the invention, the treating mixture (this term will hereinafter be used to include the methylpolysiloxane, the curing agent for the latter, aqueous medium, and any other ingredients required for obtaining emulsions or emulsion-dispersions of the methylpolysiloxane and curing agent in the aqueous vehicle) may be prepared in any suitable manner. It is preferred to employ the mixture of ingredients in the form of either an emulsion or emulsion-dispersion. The mixture of active ingredients, that is, the mixture of the methylpolysiloxane and curing agent therefor, will generally comprise from about 0.5 to 25% of the Weight of the treating composition, including all the other ingredients, particularly the water.

In making such dispersions or suspensions, various agents usually employed in such media, such as dispersing or emulsifying agents, may be used, especially where the methylpolysiloxane is easily emulsified in the water and where the metallic salt is water-soluble. Among such emulsifying agents may be mentioned, for instance, morpholene, oleate, ammonium oleate, sulfonated amide condensation products of fatty acids with organic amines, sulfonated aromatic and mixed alkylaryl sulfonate derivatives, sulfonated ester derivatives, etc. Additional satisfactory emulsifying agents are Nilo-SD (manufactured by Sandoz Chemical Works, New York, N. Y.) and Pluramine 8-100 (manufactured by Kearny Manufacturing Co., Kearny, N. 1.), both of which are fatty acid amide condensates. The actual amount of emulsifying agent employed will depend, for instance, upon the type of ingredients present in the mixture in the treating composition, the type of emulsifying agent employed, the application intended, etc. Generally, the amount of emulsifying agent satisfactorily employed may range from about 0.01 to 1.0%, by weight, based on the weight of the entire treating mixture. The amount used is not critical and persons skilled in the art will have little difiiculty in determining readily the amount which gives optimum results. it is preferable that the emulsifying agent used be one which permits the emulsion to be broken within the interstices of the leather to deposit the curable methylpolysiloxane, and which itself be reactive with the leather to prevent backwetting, e. g., Nilo SD and Pluramine 3-100.

One method for making the treating compositions herein described and which have been found so eminently useful for treating leather comprises, first, homogenizing water with the emulsifying agent until a homogeneous suspension of the emulsifying agent and water is obtained, the latter material being generally in the form of a creamy composition. To this is slowly added the methylpolysiloxane containing a small amount of an emulsion stabilizer such as, for example, oleic acid, etc. This mixture of ingredients is, in turn, again thoroughly homogenized until the rnethylpolysiloxane is intimately dispersed throughout the water phase. Finally, an additional amount of water is added to this dispersion or emulsion to bring the methylpolysiloxane content of the water emulsion to the desired level. This material is often referred to as a master emulsion. The master emulsion is then diluted with an additional amount of water containing, for instance, the water-soluble metallic salt (assuming that such a salt is employed in this description) The procedure described above for preparing water emulsions of the treating compositions herein described may, of course, be varied within wide limits, and it is not intended that the description be limiting in any manner. The presence of small amounts of organic solvents, for instance, as solvents for the metallic salts, etc., is not precluded, although usually this is not necessary. If any organic solvent is employed, it is preferable that one employ those which are easily volatilized at the temperature at which treatment of the leather will take. place. in preparing emulsions of the type described above, best results are obtained by adding stabilizers (e. g., 2-methylpentanediol-2,5 which also acts as a penetration inducer for the polymerizab'le methylpolysiloxane) for the emulsion to the diluted emulsion, usually in its final treating form, in order to avoid premature breaking of the emulsion. In addition, best uses of the emulsion are obtained if it is kept relatively cool and around room temperature. Heating of the emulsion. will also have the effect of breaking the emulsion, thereby causing the various ingredients to be deposited on the surface of the leather in a heterogeneous fashion. The above are some of the precautions which should be exercised where diiferent phases are present in the same mixture of ingredients in order to prevent separation of the phases or breakdown of the emulsion or dispersion.

On a weight basis, satisfactory results are obtained with water emulsions in which from to 99% of the emulsion or dispersion comprises water, from 1 to 20%, by weight, thereof comprises the methylpolysiloxane, and from 0.6 to 6% of the emulsion comprises the watersoluble metallic salt required to effect curing of the methylpolysiloxane.

The leathers capable of being treated in accordance with my invention are any of those available on the market and are usually advantageously treated after the raw hide is subjected to the usual conventional steps of soaking, liming, bating, pickling, tanning, sorting, splitting to weight, shaving to even, and coloring processes (the coloring can be posponed until after treatment with the curable methylpolysiloxane as long as the leather is not dried before such coloring operation), according to conventional tannery practices. There is usually another step known as fat-liquoring during which sufiicient fats and oils are introduced into the leather to cause the fibers to slide on each other, thus enabling the leather to be more flexible. Among these fats are, for instance, paraffin oil which serves as a fat for the leather. It is also possible to employ in this fat-liquoring process certain agents, such as sulfonated castor oil and/ or sulfonated cod oil which serve the purpose of imparting the desired flexibility to the leather. These latter sulfonated oils can be employed as emulsifying agents and in this respect will also serve later on in the additional capacity of supplying fat to the leather. By the use of such materials, it is possible to employ smaller amounts of the sulfonated oils in the original fat-liquoring process, relying on the subsequent emulsion treatment to supply the remaining requirements. Unexpectedly, l have found that the fat-liquoring step may be omitted and the above-mentioned methylpolysiloxane treatment used to take the place of the fat-liquoring operation to give leather products having properties comparable to those obtained using the fat-liquoring step. In addition, in contrast to the usual results obtainable with fatliquoring, the methylpolysiloxane is not leachable with water or common organic solvents.

Thereafter, the treated leather may then be drummed with the emulsion containing the fluid methylpolysiloxane and the curing agent therefor. Satisfactory treatment of the leather may be accomplished by other means such as by brushing or spraying the catalyzed emulsion on the surface of the leather, applying a solution of the catalyst to the leather followed by the treatment with the methylpolysiloxane fluid emulsion, etc. The drum is run until the emulsion satisfactorily enters the leather after which time the water is drained and the hide dried (either with or without the application of heat) to remove the residual amounts of water and to cure the methylpolysiioxane. The temperature at which the leather is treated with the emulsion may be varied. The temperature should not be too high so that the methylpolysiloxane fluid will separate out on the surface of the skin or on the inside of the drum. The particular temperature employed will vary depending upon such factors as the type of methylpolysiloxane and curing agent, concentration ofcuring agent, leather, time of curing, presence or absence of emulsion stabilizer, etc. The emulsion should be stable enough to penetrate the leather before there is any tendency of the emulsion to break so that uniform entry and treatment throughout the interstices and fibers of the leather are accomplished.

In certain types of leather, it is advantageous to prepare the tanned leather by drumming it in a dilute ammonium hydroxide aqueous solution for a period of about 15 minutes to rewet the leather. Thereafter, the leather is neutralized (e. g'., with dilute formic acid) and rinsed with water and drummed in the emulsion of the desired methylpol'ys'iloxane concentration. This drumming of the leather with the emulsion may be carried out for varying lengths of time. The drumming should be continued until the emulsion has broken in the leather and penetrated completely; this may requiredrumming from about 1 minute to about one or more'h'ours. Generally, about 5 to 45 minutes are sufiicient for the purpose. Thereafter, the drummed or treated leather is dried at room temperature or at somewhat elevated temperatures. If drying is carried out at room temperature (temperatures of about to C.), this may be accomplished by exposing the treated leather to the air for times ranging from 24 to 96 hours or more. Alternatively, elevated temperatures may be employed of the order of about 70 to 150 C. Within which range times of from about 3 to minutes, or more, may be advantageously used. One set of drying conditions comprises air-drying the treated leather for a time ranging from about 6 to 12 hours and thereafter subjecting it to a heat treatment (for instance, in a circulating oven) for about 3 to 10 minutes at about 150 C.

After treatment of the leather with the above-described emulsion and subsequent conversion of the methylpolysiloxane to the cured state by air drying or by the use of heat, it will be found that the water repellency of the leather is markedly improved and will retain this degree of water repellency even after several cycles of Washing and dry cleaning. Moreover, the leather will be permeable to air and water vapor in essentially the same amount as the leather was prior to treatment with the methylpolysiloxane emulsion. Also, the leather will be found to be greatly improved in flexibility over the untreated leather. The cro'cking properties of the leather will also be considerably improved, and the dimensional stability after several washings will be scarcely affected as a result of the treatment described above. Finally, and this is of extreme importance in the subsequent treatment of tanned leather to make, for example, suede, it will be found that in addition to the leather surface being unchanged, and being made softer, contrary to the experience encountered in using other organosilicon compositions, the surface can be easily sueded to give surfaces which are extremely soft and have good feel and handle.

The use of other organopolysiloxanes outside the scope of the critical methylpolysiloxane mixture recited above leaves a greasy film on the surface of the leather, which in addition to causing undesirable adherence of the plies of the leather, also prevent unsatisfactory sueding of the leather. Thus, the use of non-fluid, resinous methylpolysiloxanes for treating leather, or the use of methylpolysiloxane fluids substantially free of any intercondensed methyl disilane units (resulting from the presence of one or more methyl chlorodisilanes in the hydrolysis reaction) imparted to the treated leather stiif and greasy surfaces, which in some instances were undesirably tacky causing adhesion of adjacent leather plies; in each instance leather treated in this manner could not be sueded because of the poor condition of the surface. Even the employment of an emulsion of a methyl hydrogen polysiloxane widely used in the industry in treating various fibers, particularly textile materials to render the latter water-repellent, gave inferior water-repellency results. After water absorption tests were carried out on the latter treated leather, it was found that water no longer made a 90 contact angle with the flush surface of the leather indicating that the waterrepellency characteristics of the leather had pretty much disappeared.

In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts are by weight.

EXAMPLE 1 A curable methylpolysiloxane wasprepared as follows:

A mixture of ingredients containing approximately, by weight, about 5% trirnethylchlorosilane, 20% methyltrichlorosilane, 70% dimethyldichlorosilane, and about 4 to 8% of a mixture of ingredients composed of chloromethyldisilanes, particularly trichlorotrimethyldisilane and I tetrachlorodimethyldisilane, was hydrolized with water by a continuous method as is more particularly described in Schwenker patent application Serial No. 281,- 716, filed April 11, 1952, and assigned to the same assignee as the present invention, now Patent No. 2,758,124. The fluid thus obtained was neutralized with solid anhydrous sodium carbonate and filtered. Thereafter this material was stripped to remove therefrom most of the non-intercondensed volatile materials (e. g., boiling below C.) as, for instance, octamethylcyclotetrasiloxane, l1examethyl'disiloxane, etc. The stripped material amounted to about 10 or 15% of the hydrolysis product. The methylpolysiloxane fluid thus obtained was found to have a viscosity of about 100 centistokes. Thereafter, an emulsion was prepared composed of 50 parts of the above-obtained stripped methylpolysiloxane, 20 parts Water, 1 part oleic acid (as a stabilizer), and 2.5 parts of an emulsifying agent, specifically Nilo SD This mixture of ingredients was thoroughly homogenized until a thick, creamy mixture was obtained. An additional amount of 27 parts of water was added and the entire mixture again intimately mixed to give a homogeneous emulsion containing, by weight, about 50% of the methylpoly'siloxane. Samples 10 parts, by weight, of the last described emulsion were then diluted with varying amounts of water to give methylpolysiloxane Weight concentrations ranging from 1 to 8% and using zirconium acetate as a curing agent in the emulsion in an amount equivalent to 8% zirconium metal based on the weight of the methylpolysiloxane.

EXAMPLE 2 Squares (4 inches by 4 inches square weighing about 50 grams each) of chrome-tanned, bark-retanned sheepskin were drumrned' with a dilute aqueous solution of ammonium hydroxide for about 15 minutes, the ammonium hydroxide comprising about 2.5% of the weight of the leather. The drummed leather squares were rinsed in water and drummed in the above-identified silicone emulsion shown in Example 1 for about 2 hours. As a control, other squares of the above-mentioned leather were drummed in distilled water containing only zirconium acetate and free of the methylpolysiloxane emulsion. Thereafter each of the samples was removed from the drum and one set of samples treated with the emulsion was dried overnight and then heated for about 5 minutes at C. (identified as cure A). Another set of samples was merely air-dried for 72 hours at room temperature (identified as cure B). In each instance, control samples were also given the same two cures with the exception that the methylpolysiloxane emulsion was omitted and the treating was as described above, namely, in water containing only zirconium acetate. The following Table I shows the results of testing these samples for spray ratings, hydrostatic head maintained, and the percent water absorbed after several washings. The spray ratings-,which were conducted on both the grain and fiesh side of the leather, and the water absorption tests (after 20 minutes) were carried out using the methods set forth in the 1945 Year Book of the American Association of Textile Chemists and Colorists, vol. 22, pages 229 to 233 (A. A. T. C. C. test numbers 2252 and 70-52). In each instance of methylpolysiloxane treatment, the amount of the latter picked up by the leather was of the order of about 6 to 8%, of the leather.

by weight, based on the weight The treatment of the leather in accordance with the above descriptions did not destroy the hand of the leather or afiect the dimensional stability thereof. The waterrepellent film or coating on the leather fibers was entirely invisible. Attempts to treat the leather with the same methylpolysiloxane dissolved in a suitable organic solvent with a curing agent incorporated therein yielded a treated product which, after one wash, reverted to a material having a spray rating essentially the same as though it had never been treated with the methylpolysiloxane. When samples of treated and untreated sheepskin leather were drummed with an emulsion containing 2%, by weight, of the methylpolysiloxane and then subjected to a flexing test in which the material was folded and then unfolded under Water until water passage occurred through the leather, it was found that the treated leather could be flexed more than 23,000 times without any evidence of failure, while the untreated leather failed (i. 62., water passed through) after only 5000 flexes. The dimensional stability of the treated samples was greatly improved over the untreated samples. This dimensional stability, which was tested by cutting a 2-inch square from the center and washing the square a number of times and measuring the difference in dimensions after drying, showed that no discernible change in dimensions occurred even after eight washes. In contrast to this, the untreated sample, after the first Wash, showed a marked reduction in dimensions. The air and vapor permeability of the treated leather was unchanged from the untreated leather.

The leather treated in accordance with the method described in Example 2 could be readily sueded to give an extremely flexible, soft, pleasing material having a very attractive suede surface.

EXAMPLE 3 In this example, various types of leather having a varied history of preparation were treated with the same emulsion as employed in treating the leather in Example 2 with the exception that in the treatment of the polytanned kid and suede kidskin there was added to the emulsion 1%, by weight thereof, 2-methylpentanediol-2,5 for the purpose of improving the penetration of the methylpolysiloxane fluid into the interstices and fibers of the respective leathers (isopropyl alcohol, diacetone alcohol, etc., may also be used for the same purpose). This diol also unexpectedly improved the stability of the emulsion up to by weight, of the methylpolysiloxane fluid when zirconium acetate was used as the catalyst. The method of treatment was the same as that described in Example 2. In addition to subjecting the various leathers to the water absorption A. A. T. C. C. Test No. 70-52 (identified as test No. l), the chrome-tanned, bark retanned split sheepskin, polytanned kidskin, and chrome-tanned kidskin (suede kidskin) were subjected to a spray test (identified as test No. 2) which constituted a modified version of the A. A. T. C. C. Test No. 22-52. This modified test employed the same apparatus as used in the A. A. T. C. C. test, but in additional a reciprocating arm carrying a rubber covered roller was moved across the surface of the leather with a 200 gram weight pressing the roller to the leather. The water was sprayed directly in the path of the roller while mechanical action was exerted to force the Water into the leather. This test permits more reproducible results than that obtainable with A. A. T. C. C. Test No. 2252 and turnishes a better idea of the ability of the leather to withstand forced wetting by water under mechanical actionsimilar to that which is encountered in the actual use of leather garments. In carrying out the test, the leather was cut into strips 4" x 6 and weighed prior to testing. A sample was clamped into position in the apparatus and 1,000 grams water were poured through the spray funnel onto the leather during a 2 /2 minute period while the latter was being subjected to the rolling action described above. Thereafter, the leather was re-weighed and the results reported in grams of water pickup. As controls, untreated samples of the above leathers were also subjected to these various water tests; and commercially available sheepskin leather was rendered water-repellent by the use of aluminum stearate and wax. The following Table II shows the results of these two types of water pickup (or water absorption) tests on the various leathers.

It will, of course, be apparent to those skilled in the art that in addition to the specific methylpolysiloxane formulation employed above containing the recited intercondensed mcthylsiloxane units, other methylpolysiloxanes prepared from mixtures of hydrolyzable methylchlorosilanes within the proportions recited previously may also be employed without departing from the scope of the invention. It should be noted that all four ingredients, namely, the methyltrichlorosilane, trimethylchlorosilane, dimethyldichlorosilane, and mcthylchlorodisilane or mixtures of the latter disilanes, are essential for the practice of the present invention and that the optimum results are obtainable only by the presence of all these ingredients in the hydrolyzable mixture within the proportions recited previously. Also, it will be understood that other curing agents, many examples of which have been given above, may be employed and that other leathers in addition to those recited above may be used within the scope of this invention.

The incorporation of other additives ordinarily employed in leather treatment is not precluded. Thus, if desired, one may also incorporate in the emulsion containing the methylpolysiloxane various plasticizers, bonding agents, etc. These plasticizers generally are any one of those commonly used for commercial purposes including such compounds as parafiin oil, paraifin wax, neetsfoot oil, tricresyl phosphate, dimethyl phthalate, etc. Agents for the purposes of improving the bond between the methylpolysiloxane and the leather may also be added,

although their use is not generally necessary since the methylpolysiloxane fluid apparently bonds quite satisfac torily to the leather after the curing has been carried out.

Other resins which do not adversely affect the emulsion or are not adversely affected by the metallic salt may be incorporated and used in conjunction with the methylpolysiloxane in the emulsion, for instance, polystyrene, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polymethylmethacrylate, etc.; drying oils such as chinawood oil, oiticica oil, linseed oil, etc., may also be employed without departing from the scope of the invention.

After treatment of the leather to render it water-- repellent in accordance with my invention, the leather may be finished in any manner desired employing various materials generally used to improve the appearance, scuff resistance, modify the color of the leather, etc. Finishing materials widely employed for this purpose include alkyl polyacrylate (or polymethacrylate) emulsions in conjunction with natural or synthetic rubber latices. I have found that improved adhesion of the latter finishing materials may be achieved by priming the methylpol siloxane coated leather surface (or any leather surface coated or impregnated with other organopolysiloxanes) with various organic silicates or partially hydrolyzed organic silicates in the manner more particularly described in Smith-Johannsen Patent 2,643,964, issued June 30, 1953, and assigned to the same assignee as the present invention. Without the organosilicate priming, the finish on the leather is undesirably affected by abrasion, or else will tend to adhere and be removed when adhesive materials such as adhesive tapes are applied to the leather finish and then removed therefrom. In general, this priming action of the water-repellent leather may be accomplished by treating the latter with solutions of the organesilicate (or partially hydrolyzed organosilicate) containing from about 3 to by Weight, or more of the organosilicate. I have found that an 8%mineral spirits solution of a partially hydrolyzed ethyl silicate, when used to treat the above-described water-repellent leather is suflicient for the purpose of incorporating from 0.01 to 0.1% of the ethyl silicate, based on the weight of the leather, and that this amount of organic silicate is sulficient for improving the adhesion of the finishing material to the water-repellent leather substrate.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The process for improving the water-repellency properties of leather, which comprises treating the latter With an aqueous emulsion containing as the essential treating agent a mixture of ingredients comprising (a) the polymerizable, fluid, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by Weight, of 50 to 75% dimethyldichlorosilane, 1 to 10% trimethylchlorosilane, 10 to 35 methyltrichlorosilane, and from 1 to 10% of a methyl-chlorodisilane and (b) a curing agent for (a) comprising a metal lic salt of an acid whose metal ion is present, by weight, in an amount equal to at least 2%, based on the weight of the aforesaid hydrolysis product, the amount of the said hydrolysis product ranging from 0.2 to by weight, of the total weight of the aqueous emulsion.

2. The process for improving the water-repellency properties of leather which comprises (1) treating the latter with an aqueous emulsion containing as the essential treating agent a mixture of ingredients comprising (a) the polymerizable, fluid, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by weight, of 50 to 75% dimethyldichlorosilane, 1 to 10% trimethylchlorosilane, 10 to 35% methyltrichlirosilane and from 1 to 10% of a mixture of methylchlorodisilanes containing tetrachlorodimethyldisilanes, pentachloromethyldisilane, and trichlorotrimethyldisilane and (b) a curing agent for (a) comprising zirconium acetate in which the zirconium is present, by weight, in an amount equal to from 2 to 14%, based on the weight of the aforesaid hydrolysis product, the amount of the said hydrolysis product ranging from 0.2

to 20%, by weight, of the total weight of the aqueous emulsion, and (Z) drying the leather.

3. The process for improving the Water-repellency properties of leather Which comprises (1 treating the latter with an aqueous emulsion containing as the essential treating agent a mixture of ingredients comprising (a) the polymerizable, fluid, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by Weight, of 50 to dimethyldichlorosilane, l to 10% trimethylchlorosilane, 10 to 35% methyltrichlorosilane and from 1 to 10% of a mixture of methylchlorodisilanes containing tetrachlorodimethyldisilane and pentachloromethyldisilane, and (b) a curing agent for (a) comprising zirconium nitrate in which the zirconium is present, by Weight, in an amount equal to from 2 to 14%, based on the weight of the aforesaid hydrolysis product, the amount of the said hydrolysis product ranging from 0.2 to 20%, by weight, of the total Weight of the aqueous emulsion, and (2) drying the leather.

4. The process as in claim 1 in which the aqueous emulsion used to treat the leather comprises, by Weight, from to 99% water, from 1 to 20% of the polymerizable, fluid, intercondensed product of hydrolysis of the mixture of methylchlorosilane, and from 0.06 to 6% of the metallic salt.

5. The process as in claim 2 in which the emulsion used to treat the leather comprises, by weight, from 80 to 99% Water, from 1 to 20% of the polymerizable, fluid, intercondensed product of hydrolysis of the mixture of methylchlorosilanes, from 0.06 to 6% of the zirconium acetate, and a small amount of an emulsifying agent.

6. The process as in claim 3 in which the emulsion used to treat the leather comprises, by weight, from 80 to 99% Water, from 1 to 20% of the polymerizable, fluid, intercondensed product of hydrolysis of the mixture of methylchlorosilanes, from 0.06 to 6% of the zirconium nitrate, and a small amount of an emulsifying agent.

7. A leather article obtained in accordance with the process of claim 1.

8. A leather article obtained in accordance with the process of claim 2.

9. A leather article obtained in accordance With the process of claim 3.

10. A leather treating emulsion composition adapted for imparting improved water repellency, washability and flexibility to leather which comprises, by weight, (a) from 80 to 99% Water, (b) from 1 to 20% of a polymerizable, fluid, non-resinous, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by Weight, of 50 to 75% dimethyldichlorosilane, l to 10% trimethylchlorosilane, 10 to 35% methyltrichlorosilane, and from 1 to 10% of a methylchlorodisilane, (c) from 0.06 to 6% of a curing agent for (b) comprising a metallic salt of an acid and (d) an emulsifying agent.

11. A leather treating emulsion composition adapted for imparting improved water repellency, washability, and flexibility to leather which comprises, by Weight (a) from 80 to 99% Water, (12) from 1 to 20% of a poly: merizable, fluid non-resinous, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed essentially, by weight, of 50 to 75% dimethyldichlorosilane, 1 to 10% trimethylchlorosilane, 10 to 35 methyltrichlorosilane, and from 1 to 10% of a methylchlorodisilane, (c) from 0.06 to 6% zirconium acetate and (d) an emulsifying agent.

12. A leather treating emulsion composition adapted for imparting improved water repellency, washability, and flexibility to leather which comprises, by weight, (a) from 80 to 99% water, (b) from 1 to 20% of a polymerizable, fluid, non-resinous, intercondensed product of hydrolysis of a mixture of methylchlorosilanes composed 13 essentially, by weight, of 50 to 75% dimethyldichlorosilane, 1 to 10% trimethylchlorosilane, 10 to 35% methyltrichlorosilane, and from 1 to 10% of a methylchlorodisilane, (c) from 0.06 to 6% zirconium nitrate, and (d) an emulsifying agent.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE PROCESS FOR IMPROVING THE WATER-REPELIENCY PROPERTIES OF LEATHER, WHICH COMPRISES TREATING THE LATTER WITH AN AQUEOUS EMULSION CONTAINING AS THE ESSENTIAL TREATING AGENT A MIXTURE OF INGREDIENTS COMPRISING (A) THE POLYMERIZABLE, FLUID, INTERCONDENSED PRODUCT OF HYDROLYSIS OF A MIXTURE OF METHYLCHLOROSILANESE COMPOSED ESSENTIALLY, BY WEIGHT, OF 50 TO 75% DIMETHYLDICHLOROSILANE, 1 TO 10% TRIMETHYLCHLOROSILANE, 10 TO 35% METHYL TRICHLOROSILANE, AND 1 TO 10% OF A METHYLCHLORODISILANE AND (B) A CURRENT FOR (A) COMPRISING A METALLIC SALT OF AN ACID WHOSE METAL ION IS PRESENT, BY WEIGHT, IN AN AMOUNT EQUAL TO AT LEAST 2%, BASED ON THE WEIGHT OF THE AFORESAID HYDROLYSIS PRODUCT, THE AMOUNT OF THE SAID HYDROLYSIS PRODUCT RANGING FROM 0.2 TO 20%, BY WEIGHT, OF THE TOTAL WEIGHT OF THE AQUEOUS EMULSION. 